The effect of freezing rate on striped bass (Morone saxatilis) spermatozoa

Abstract

Several studies have attempted to determine the optimal freezing rate for the cryopreservation of striped bass spermatozoa. In this study, the effects of freezing rate (-10, -15, -20 and -40oC/min) on sperm quality was examined utilizing Sybr-14/Propidium Iodide staining to confirm membrane integrity, a luciferin-luciferase assay to estimate ATP concentration and a Hamilton-Thorne CEROSTM system to characterize sperm motion. Males (n=12) were sampled once a week for five weeks. Samples were extended, cryo-protected using a 7.5% (v/v) dimethyl sulfoxide solution, and frozen using a controlled-rate freezer. Samples were stored in liquid nitrogen for 49 days and re-evaluated post-thaw. Sperm cryopreserved at -40oC per minute resulted in: total motility (10.06%), progressive motility (7.14%), ATP concentration (0.86 pmol/million cells), and sperm viability (56.5%); which were greater (P < 0.05) than the slower rates. Results demonstrate that -40oC/minute was the optimal freezing rate among those tested for the cryopreservation of striped bass spermatozoa.